In normal power generation facilities using geothermal heat, the ground is excavated to a predetermined depth and a geothermal fluid in which vapor and hot water coexist under a high pressure in a deep underground is emitted to the ground. The geothermal fluid is separated into vapor and hot water by a vapor-water separator, and this separated vapor drives and rotates a turbine for power generation.
However, the hot water and vapor taken out from a deep underground usually contain gas components such as carbon dioxide (CO2), hydrogen sulfide (H2S), ammonia (NH3), and methane (CH4). Sodium chloride (NaCl), boron (B), arsenic (As) and mercury (Hg), for example, are contained as chemical components depending on a temperature. When these gas components and chemical components are released on the ground, they can be a cause of pollution. Accordingly, after a turbine is driven and rotated, it is not preferable to release the used vapor into the atmosphere in view of the global environment. Furthermore, impurities need to be processed, resulting in increasing facility costs as well as causing the facilities to be complicated. To prevent depletion of the geothermal fluid, the separated hot water and used vapor need to be cooled and returned to the underground, and this also results in increasing facility costs.
In view of the above problems, there has been proposed an apparatus of supplying water from the ground to the underground, heating this water by geothermal heat to take it as vapor, and driving and rotating a turbine by the vapor for power generation, instead of taking out a geothermal fluid (vapor) in a deep underground to the ground. Such a power generation apparatus is described in Patent Literatures 1 and 2, for example.
According to the apparatuses described in these Patent Literatures, a sealed piping in which a water intake pipe is placed so as to surround a water supply pipe is provided in the ground, water supplied through the water supply pipe is heated by geothermal heat at a lower heat exchange unit, the heated fluid is taken out to the ground through the water intake pipe, and vapor is separated therefrom by a vapor-water separator to drive and rotate a turbine.